1. Field of the Invention
The present invention relates to an engine that is favorable for use in an airplane, a flying body, a space shuttle or a space rocket, wherein liquid hydrogen is used as fuel and oxygen in air is used as an oxidizing agent while it is being liquefied.
2. Description of the Prior Art
A space rocket must carry an oxidizing agent for burning fuel in addition to the fuel, because normally it flies through a cosmic space where no air is present. Rockets of recent years which make use of liquid hydrogen as fuel and liquid oxygen as an oxidizing agent are practically useful.
However, in practicality, the amount of fuel and oxidizing agent required (fuel and oxidizing agent will hereinafter be referred to collectively as "propelling agent") is such that they occupy the largest part of the weight and volume of the main body of the rocket. As a result, the weight of a payload, such as human bodies and artificial satellites, is limited. If the weight of such payload is increased, it will be necessary to correspondingly increase the amount of propelling agent carried. This will, in turn, necessitate reinforcement of the rocket structure in proportion to the increase of the weight of the payload and the propelling agent. In addition, it is necessary to provide more propelling agent for launching the added weight of the payload, the propelling agent and the reinforcement structure members. Thus, increasing the weight of the payload results in an enormous expense.
In light of these problems, the inventors of the present invention have previously invented a lightweight engine having an excellent oxygen liquefying efficiency and which can efficiently utilize oxygen in the atmosphere as an oxidizing agent at least during flight in the atmosphere, in order to cut or reduce the weight of the oxidizing agent. This invention is set forth in Japanese Patent Application No. Sho 59 (1984)-180759, and will now be explained with reference to FIGS. 5 and 6.
At first, as shown in FIG. 5, liquid hydrogen at a temperature in the proximity of its triple point (about 14.degree. K.) stored in a liquid hydrogen tank 1 is pressurized by means of a pump 3 and is fed into an air condensor 5. The air condensor 5 is a heat-exchanger composed of flat plates or finned tubes and condenses and liquefies air by making use of a coolant consisting of low-temperature hydrogen.
In the air condensor 5, the liquid hydrogen has its temperature raised by being exposed to the condensation heat of air, and is then fed into an air precooler 7. The air precooler 7 is provided to preliminarily cool the air introduced through an air duct 14 to about 90.degree. K. for the purpose of enhancing the air liquefying efficiency of the air condensor.
It is to be noted that since the liquefying temperature and the efficiency for liquefying air will change depending upon the pressure thereof, in the case where the rocket operates high up in the air at a high speed, the pressures in the air precooler 7 and the air condenser 5 should be raised appropriately by means of a ram pressure device or the like.
Liquid hydrogen having come out of the air precooler 7 is led through a pipe 8 to a combustor 19 of the rocket engine.
On the other hand, liquid oxygen at a temperature in the proximity of its triple point (about 55.degree. K.) stored in a liquid oxygen tank 9 is pressurized by means of a pump 11 and is led into a head portion of the air condenser 5. The liquid oxygen in the air condensor 5 is then sprayed in a shower-like manner into an air flow within an air duct 15 by means of a sprayer 13 so as to liquefy the air.
The condensed and liquefied air in the condensor 5 (the air having been liquefied by the coolants consisting of hydrogen and liquid oxygen) is mixed with the sprayed liquid oxygen, and after being pressurized by a pump 17, is fed to the combustor 19 of the rocket engine.
In the combustor 19, combustion is effected by the mixed fluid consisting of the fed liquid hydrogen, the liquefied air and the liquid oxygen. In this manner, high-temperature combustion gas is ejected through a nozzle and a propelling force is generated.
As described above, in the rocket engine shown in FIG. 5, the amount of liquefaction of the air is increased by spraying the low temperature liquid oxygen coolant from the sprayer 13, thereby raising the liquefying temperature due to the increase in the oxygen concentration of the air. Accordingly, the propelling force of the rocket engine is improved.
In an example of the prior art shown in FIG. 6, the construction is similar to that shown in FIG. 5, except that an axial flow type or centrifugal type air compressor 21 is added downstream of the air flow in the air condensor 5, and an auxiliary air condensor 23 is added downstream of the air compressor 21. This auxiliary air condensor 23 is cooled by hydrogen having a temperature of about 80.degree. K. fed from the air condensor 5.
In this example of the prior art, any remaining gaseous air (i.e. that which has not been liquefied in the air condensor 5) is compressed by the air compressor 21 to raise its pressure. Such compressed air is then led into the auxiliary air condensor 23.
The liquefying temperature (boiling point) of air will, of course, rise in accordance with a rise in pressure. In the engine shown in FIG. 6, since there are provided the air compressor 21 and the auxiliary condensor 23, the pressure of the air will rise. As a result, the liquefying temperature will increase and the amount of latent heat of liquefaction will decrease, thereby causing the amount of liquefaction to increase.
In addition, in FIGS. 5 and 6, reference numerals 2, 4, 6 and 6' designate liquid hydrogen pipes, numerals 10 and 12 designate liquid oxygen pipes, numerals 16 and 18 designate liquid air pipes, and numerals 20 and 22 designate air pipes.
In an air liquefaction cycle engine which employs the oxygen in air as an oxidizing agent while it is liquefying the air, the performance is determined by the magnitude of the amount of liquefied air produced by an air liquefier. Accordingly, an air liquefaction cycle engine can be improved by increasing the amount of liquefied air produced. In the prior art rocket engines shown in FIGS. 5 and 6, only liquid oxygen and liquid hydrogen are relied upon as coolants for air liquefaction. Since the amount of liquid oxygen and liquid hydrogen is finite, the amount of liquefied air is correspondingly limited.